Like so many, I’ve been absolutely appalled by the horrific nature of the Plymouth nursery abuse case: but I have not been surprised.

As a former detective specialising in child protection and now as a private consultant in the same field, I’ve got 20 years of experience telling me that this was an outrage waiting to happen.

Ask anyone to describe their idea of a paedophile and almost all of them will begin with the word ‘he’.

But that’s simply not always correct, as this case has made so shockingly clear. Yes, the vast majority of paedophiles are men but even official estimates admit that 6 to 10 per cent of them are women.

Yet I believe those figures seriously under-estimate the true extent of female paedophilia; a more accurate estimate could be 15 to 20 per cent and, thanks to the internet, that figure could be rising.

The idea of women sexually abusing children in their charge is abhorrent to us all. How can it possibly be true?

But it is true, albeit in only a very small number of cases, and made easier for these women by the fact that they have access to children and, perhaps, most importantly of all, because we trust them implicitly.

And that, in turn, makes it so much more difficult for their young victims to raise the alarm. If a child came back from nursery complaining about a man having done something unusual to them, our suspicions would be raised in an instant.

But if they come back saying the nice, plump, smiley girl who looks after them has done something odd, we’d immediately assume our child had simply got the wrong end of the stick. Until the sordid events of this week.

I believe the sexual abuse of children by women is such an under-reported crime – by and large, we simply don’t believe it happens. But, as we all now know, it does.

There are, however, some key differences in the way male and female paedophiles behave, as this case shows.

Women seem to be abusing much younger children, even babies, and, unlike their male counterparts, they nearly always do so in cahoots with another male or female.

And that’s because the motivation isn’t usually their own sexual gratification – although in a few truly deviant cases it may be – they are seeking the approval of their partner-in-crime.

The email detailing a plot to abduct a child from a railway station showed this –Vanessa George did what she did to earn the approval, even respect of the evil couple egging her on.

Perhaps for the first time in her life, her ability to supply these awful images made her feel powerful and wanted.

The case also confirms some of my darkest fears about the internet.

Not only does it make it clear that there is the strongest possible link between viewing child pornography online and a child being abused for real, it shows what a horrifyingly powerful tool the internet has become in bringing sexually deviant minds together.

Before the internet, it might have taken a paedophile like Colin Blanchard decades to find a woman who not only shared his sexual interest in children but was prepared to facilitate it. Now two such women proved to be only a couple of clicks away.

Given that female paedophiles prefer to act as part of a partnership or team, that’s a hugely worrying development.

What the Plymouth case makes clear is that a lot more research needs to be done into female paedophiles. The vast majority of male paedophiles caught by police on the internet have no previous convictions.

Police find, on average, they will have been attempting to abuse children, or viewing online child pornography for six years and in 70 per cent of cases will have abused between one and five different children.

Do the same statistics apply to female paedophiles? We don’t know but given that Vanessa George had no criminal record we certainly need to find out.